Preparation of o,o-dimethyl-thionophosphoric acid {8 o-quinoxalyl-(2){9 {0 ester

ABSTRACT

The invention concerns a novel process for the production of O, O-dimethyl-thionophosphoric acid (O-quinoxalyl-(2)) ester of the formula: The compound is an insecticide and acaricide.

United States Patent Gagnaux [451 July 18,1972

[54] PREPARATION OF 0,0-DIMETHYL- THIONOPHOSPHORIC ACID [0-QUINOXALYL-(2)] ESTER [72] Inventor:

[73] Assignee:

Pierre Gagnaux, Bottmingen, Switzerland Sandoz Ltd., (also known asSandoz AG), Basel, Switzerland [22] Filed: Jan. 20, 1970 [21] Appl.No.:4,423

[58] Field of Search ..260/250 R [56] References Cited FOREIGN PATENTSOR APPLICATIONS 1,081,249 8/1967 Great Britain ..260/2S0 R 1,085,3409/1967 Great Britain ..260/250 R Primary ExaminerNicholas S. RizzoAttorney--Gerald D. Sharkin, Robert S. Honor, Frederick H. Weinfeldt,Richard E. Vila and Walter F. Jewell [5 7] ABSTRACT The inventionconcerns a novel process for the production of0,0-dimethyl-thionophosphoric acid [O-quinoxalyl-( 2)] ester of theformula:

The compound is an insecticide and acaricide.

3 Claims, No Drawings PREPARATION OF 0,0-DIMETIIYL- TI'IIONOPIIOSPHORICACID [O-QUINOXALYL-(ZH ESTER The present invention relates to a processfor the production of 0,0-dimethyl-thionophosphoric acid[O-quinoxalyl-(Z ester of formula I.

According to the invention, there is provided a process for theproduction of 0,0-dimethyl-thionophosphoric acid quinoxalyl-(2)] ester,which comprises reacting a compound of formula II,

in which Z signifies sodium or potassium, with0,0-dimethylthionophosphoric acid halide of formula III,

CH30 S CHsO III in which X signifies a halogen atom, in the presence offrom 0.01 mol to 0.8 mols calculated on the amount of2hydroxyquinoxaline, of a tertiary heterocyclic or tertiary aromaticamine catalyst, in an inert polar solvent.

The cation Z is preferably sodium and the halogen atom X is preferablychlorine.

Polar solvents especially suitable for the process of the invention areacetone and acetonitrile.

Heterocyclic tertiary amines, e.g. pyridine, or aromatic tertiary aminesmay be used as catalysts. A good yield is obtained with the addition ofabout 0.01 mol of the catalyst, calculated on the amount of2hydroxy-quinoxaline. In general when a larger amount of catalyst isadded smaller yields of the desired product are obtained.

The reaction temperature may vary considerably. A temperature between 20and the boiling point of the mixture, preferably between 20 and +50 C.

The 0,0-dimethyl-thionophosphoric acid [0-quinoxalyl-(2)] ester obtainedin accordance with the process of the invention is a crystallinecompound having a sharp melting point, which may be purified byrecrystallization from the usual solvents.

The 0,0-dimethyl-thionophosphoric acid [0-quinoxalyl-(2)] ester obtainedin accordance with the process of the invention is a useful insecticideand acaricide and is of low toxicity in warm-blooded animals.

The compound of formula 1 may be used as such in agriculture, inbuildings, e.g. inhabited rooms, cellars, attics, stables, etc., and inprotecting plants and also animals against insects and acarids.

The compound of formula 1 may be applied to its use on its own or inadmixture with a suitable diluent, carrier or adjuvant. The compound maybe applied to the required locus, e.g. a field of growing plants or anorchard, using conventional applicator equipment. Accordingly,formulations containing the compound of formula 1 and comprisingspraying agents, dusting agents, wettable powders or emulsifiableconcentrates may be prepared. A formulation conveniently contains about0.01 to about 2 percent by weight of the compound of formula I togetherwith one or more conventional wetting, emulsifying or dispersing agents.

The following Examples are illustrative of the invention, but in no waylimit the scope thereof.

EXAMPLE 1:

219 g (1.5 mols) of l,2-dihydro-2-oxoquinoxaline are boiled under reflux(with a water separator) together with 60 g (1.5 mols) of sodiumhydroxide powder in 2000 cc of xylene while stirring, until completedehydration has taken place. Cooling to room temperature is effected,the sodium salt is filtered ofi with suction, is washed with benzene anddried in a vacuum at 70.

48 g of 0,0-dimethyl-thionophosphoryl chloride are added dropwise atroom temperature while stirring during the course of 30 minutes to amixture of 51 g of the sodium salt of 1,2- dihydro-2-oxo-quinoxalinewith 300 cc of acetonitrile and 1.5 cc of pyridine. The reaction mixtureis further stirred for 3% hours, is cooled to 0 and filtered withsuction. The filtrate is subsequently concentrated in a vacuum in awater bath at 50 and the oily residue poured on ice water. After a fewminutes the precipitated, solid product is filtered off by suction anddissolved in cc of acetone while moist. The solution is stirred for ashort time with 12 g of active charcoal, is subsequently filtered andthe filtrate is poured into a mixture of 500 cc of ice water and 60 ccof a 10 percent caustic soda solution while stirring. After stirring for20 minutes, the solid product is filtered off by suction, is againwashed with water and dissolved in 280 cc of benzene. A small aqueouslayer is separated and the benzene solution is evaporated to dryness ina water jet vacuum on a water bath (50). The evaporation residue becomessolid after standing at room temperature for several hours. 61.5 g 75percent of the theoretic yield of 0,0- dimethyl-thionophosphoric acid[0-quinoxalyl-(2)] ester having a melting point of 45-47 are obtained.

Analysis: C H N ,O PS C found 44.5%

calculated 44.8%

Molecular weight: 27025 N found 10.4% P found 11.5% calculated 9.8%calculated 1 1.7%

What is claimed is:

l. A process for the production of 0,0-dimethylthionophosphoric acid[0-qunioxalyl-( 2)] ester of the formula:

S OCH:

which comprises reacting an alkali metal salt of 2-hydroxyquinoxaline ofthe formula:

wherein Z is sodium or potassium, with 0,0-dimethylthionophosphoric acidhalide of the formula:

CHaO

solvent is acetone or acetonitrile.

a a a a a

2. A process according to claim 1, wherein Z signifies sodium and Xsignifies chlorine.
 3. A process according to claim 1, wherein the inertpolar solvent is acetone or acetonitrile.